Determining Residual Effects of Isoproturon Applied at Graded Levels through Bioassay and Analytical Procedures

Isoproturon was applied at 0.47, 0.94, 1.88, 2.82 and 3.76 kg ha⁻¹ to pots during 1995–96 and 1997–98 at the experimental farm of Punjab Agricultural University, Ludhiana. Residual concentration of isoproturon estimated by adopting bioassay technique indicated that growth and development of muskmelon var. Hara Madhu (particularly dry matter/pot) upto 0.94 kg ha⁻¹ (recommended dose) was statistically at par with control pots, whereas higher levels of isoproturon showed phyto-toxicity on test plant. However, no phyto-toxicity on maize and moong was observed even at higher levels of isoproturon. Residual concentration determined by analytical techniques indicated that 60 tu 90 days were required for the complete degradation of isoproturon depending upon its level of application i. e. from 0.47 kg ha⁻¹ (1/2 the recommended) to 3.76 kg ha⁻¹ (four times).